1. Technical Field
This invention relates generally to touch sensors, and more particularly to a touch sensor suitable for use in an electronic device.
2. Background Art
Portable electronic devices such as mobile telephones and personal digital assistants are becoming more sophisticated due to advancing technology. For example, until recently, the user interface for a mobile telephone included twelve to fifteen mechanical buttons. Today, however, many portable devices include full QWERTY keypads. While these keypads are often quite small, users can become proficient with their use, and type almost as fast as with a full-size QWERTY keypad.
Larger electronic devices, such as laptop computers, employ the use of touch pads for navigation in addition to the standard QWERTY keypad. By using a touch pad, users can move a cursor around the display to manipulate objects, navigate between applications, and actuate icons and other actuation targets. Some touch pads even facilitate the use of multi-touch gestures to more efficiently manipulate objects on the display.
With the increasing functionality of smaller devices, it would be desirable to add touch pads to mobile telephones and personal digital assistants. However, frequently there is simply not enough real estate on the surface of a compact device to accommodate a touch pad. This is especially true in a QWERTY keypad enabled device designed to be small enough to fit within a pocket.
Some devices include touch sensitive displays instead of touch pads. With a touch sensitive screen, the user touches a plastic or glass surface atop the display. Touch sensing circuits such as capacitive touch sensors then determine the location of the user's finger. While these devices work well in practice, they are not without issues. When a user touches the display, the finger invariably renders a portion of the display non-visible.
There is thus an opportunity to develop a user interface that supports touch manipulation that neither requires additional device surface area nor results in an obstructed view of the display.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.